Resonant Tunneling Diodes for Sub-Terahertz and Terahertz Oscillators

TLDR

Resonant tunneling diodes can serve as compact, coherent terahertz sources that operate at room temperature. The study presents sub‑THz and THz oscillators that integrate RTDs on planar circuits. The authors analyze frequency and power limits from tunneling, transit‑time, and parasitic effects, and describe coherent power combining and injection locking in array configurations. They demonstrate room‑temperature oscillations up to 0.65 THz (fundamental) and 1.02 THz (harmonic), confirm size‑dependent frequency behavior, predict achievable 2.3 THz and 60 µW at 1 THz with improved designs, observe voltage‑controlled oscillation, and show coherent power combining and injection locking.

Abstract

Resonant tunneling diodes (RTDs) have the potential for use as compact and coherent terahertz (THz) sources operating at room temperature. In this paper, sub-THz and THz oscillators with RTDs integrated on planar circuits are described. Fundamental oscillation up to 0.65 THz and harmonic oscillation up to 1.02 THz were obtained at room temperature in our recent study. Limiting factors for oscillation frequency and output power are theoretically analyzed including tunneling and transit-time effects and parasitic elements. Oscillation frequency and its dependence on RTD size are in good agreement with the measured results. Based on this result, it is shown that fundamental oscillation up to 2.3 THz and an output power of 60 µW at 1 THz are theoretically expected by improving the structures of the RTD and the antenna. Voltage-controlled oscillation, which is useful for the precise control of frequency, is observed in the RTD oscillators. Coherent power combining in an array configuration to achieve high output power as well as mutual injection locking between the array elements are also described.